The present invention relates to a process for the impregnation of an aluminum alloy with a surface comprising a hard wear-resistant material.
A wide variety of techniques are known for the impregnation of iron with a hard wear-resistant surface. Such techniques include flame spray coating and plasma spray coating. However, each of these spray coating techniques suffer from problems associated with the spalling of surface layers during the coating process and during service as well as the particularly large expense associated with the use of these techniques.
Cast-In-Carbides are also known in which carbide particulate are placed within a mold and molten iron is then cast. See, for example, the discussion within U.S. Pat. No. 4,119,459 to Ekemar et al. It is difficult, however, with such castings to accurately maintain the carbide particles in the desired location and in a regular distribution pattern.
In addition, certain cast-on hard surfacing techniques for use with polystyrene patterns are also known in the art. See, for example, the discussion in Hansen et al, "Application of Cast-On Ferrochrome-Based Hard Surfacings to Polystyrene Pattern Castings," Bureau of Mines Report of Investigations 8942, U.S. Department of the Interior, 1985.
While those methods have been used for the impregnation of iron, they have not heretofore been employed with aluminum alloys. The art has instead made composite materials from aluminum having a cylindrical shape by centrifuging a slurry of molten aluminum and fine carbide particles such that either the metal or the carbides segregate preferentially to the outer circumference of the cylinder so as to yield the higher concentration of that respective phase.
However, such a method would be unsuitable for casting heavy carbides, such as tungsten carbide, whose density is more than five times that of aluminum since it would be impractical to hold these heavy particles in suspension. Furthermore, such a method would not be effective in introducing a hard wear resistant surface into selective areas of the casting as well as casting complex aluminum shapes which are desirably impregnated with a wear resistant material.
Accordingly, the need still exists for a method of impregnating aluminum alloy surfaces with a hard wear-resistant material.